Apparatus with data reader sensors more recessed than servo reader sensor

ABSTRACT

An apparatus according to one approach includes a servo reader transducer structure on a module. The servo reader transducer structure has a lower shield, an upper shield above the lower shield, the upper and lower shields providing magnetic shielding, a current-perpendicular-to-plane sensor between the upper and lower shields, an electrical lead layer between the sensor and one of the shields, and a spacer layer between the electrical lead layer and the one of the shields. The electrical lead layer is in electrical communication with the sensor. The conductivity of the electrical lead layer is higher than the conductivity of the spacer layer. An array of writers is also present on the module. Writer modules having this structure are less susceptible to shorting, and therefore enable use of TMR servo readers on writer modules.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to magnetic heads, e.g., magnetictape heads, which include current-perpendicular-to-plane (CPP) servosensors having hard spacers incorporated therewith.

In magnetic storage systems, magnetic transducers read data from andwrite data onto magnetic recording media. Data is written on themagnetic recording media by moving a magnetic recording transducer to aposition over the media where the data is to be stored. The magneticrecording transducer then generates a magnetic field, which encodes thedata into the magnetic media. Data is read from the media by similarlypositioning the magnetic read transducer and then sensing the magneticfield of the magnetic media. Read and write operations may beindependently synchronized with the movement of the media to ensure thatthe data can be read from and written to the desired location on themedia.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape, and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly for use in such systems.

In a tape drive system, the drive moves the magnetic tape over thesurface of the tape head at high speed. Usually the tape head isdesigned to minimize the spacing between the head and the tape. Thespacing between the magnetic head and the magnetic tape is crucial andso goals in these systems are to have the recording gaps of thetransducers, which are the source of the magnetic recording flux in nearcontact with the tape to effect writing sharp transitions, and to havethe read elements in near contact with the tape to provide effectivecoupling of the magnetic field from the tape to the read elements.

Tunneling magnetoresistive (TMR) servo readers are susceptible toscratching caused by contact with asperities fixed on moving magneticmedium surfaces. Friction between asperities on the tape and the ductilemetallic films in the sensor gives rise to deformation forces in thedirection of tape motion. As a result, an electrical short is oftencreated by the scratching and/or smearing of conductive material acrossthe layers, which has a net effect of creating bridges of conductivematerial across the sensor. Particularly, particles protruding from themedium tend to plow through ductile magnetic material, e.g., from one orboth shields, smearing the metal across the insulating material of thesensor, and thereby creating an electrical short that reduces theeffective resistance of the sensor and diminishes the sensitivity of thesensor as a whole. Deep scratches may result in electrical shorting dueto abrasive lapping particles that scratch or smear conductive materialacross the insulating materials separating the conductive leads, e.g.,opposing shields, which allow sense (bias) current to flow through thesensor and magnetic head as a whole. The scratches may result in a lossof amplitude and track following ability. When electrical shortingoccurs in a servo reader of the writing module, the head containing thewriting module may become non-functional for writing operations in atleast one tape motion direction, and possibly in both directions.

Susceptibility to scratching and problems arising from scratching inconventional TMR servo reader sensors has precluded adoption of TMRservo reader sensors in writing modules. Giant magnetoresistive (GMR)servo readers are conventionally used in writing modules.Problematically, GMR servo readers must be wider than TMR servo readersto have adequate output. Wide GMR sensors are not able to resolve trackposition as well as narrower TMR sensors. GMR sensors have lowersensitivity than TMR sensors. Further, GMR sensors may exhibitnon-uniform and/or unstable magnetic response across the width of thetrack leading to relatively less precise positioning of tracks on tapeand limiting how densely tracks may be shingled. The use of GMR sensorslimits tracks per inch (TPI) growth.

GMR sensors are also susceptible to degradation and declining outputwith usage due to changes (e.g., due to interdiffusion) in thesensitive, thin copper spacer layer and/or to changes in crystalstructure of the antiferromagnetic (AFM) layer in the GMR stack.

SUMMARY

An apparatus according to one approach includes a servo readertransducer structure on a module. The servo reader transducer structurehas a lower shield, an upper shield above the lower shield, the upperand lower shields providing magnetic shielding, acurrent-perpendicular-to-plane sensor between the upper and lowershields, an electrical lead layer between the sensor and one of theshields, and a spacer layer between the electrical lead layer and theone of the shields. The electrical lead layer is in electricalcommunication with the sensor. The conductivity of the electrical leadlayer is higher than the conductivity of the spacer layer. An array ofwriters is also present on the module. Writer modules having thisstructure are less susceptible to shorting, and therefore enable use ofTMR servo readers on writer modules.

Such structures are especially beneficial when the sensor is a tunnelingmagnetoresistive servo sensor.

In some approaches, an electrical lead layer and spacer layer arepresent between the sensor and each shield, thereby enhancingreliability by providing protection against shorting for bi-directionaltape operation.

The aforementioned enhanced reliability also enables minimal recessionof the current-perpendicular-to-plane sensor from the plane of the mediafacing surface of the module, and consequently less spacing loss whenreading servo tracks. For example, the recession of thecurrent-perpendicular-to-plane sensor from the plane is about 5 nm orless in some approaches.

Any of these approaches and embodiments may be implemented in a magneticdata storage system such as a tape drive system, which may include amagnetic head, a drive mechanism for passing a magnetic medium (e.g.,recording tape) over the magnetic head, and a controller electricallycoupled to the magnetic head.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of a simplified tape drive systemaccording to one approach.

FIG. 1B is a schematic diagram of a tape cartridge according to oneapproach.

FIG. 2 illustrates a side view of a flat-lapped, bi-directional,two-module magnetic tape head according to one approach.

FIG. 2A is a tape bearing surface view taken from Line 2A of FIG. 2.

FIG. 2B is a detailed view taken from Circle 2B of FIG. 2A.

FIG. 2C is a detailed view of a partial tape bearing surface of a pairof modules.

FIG. 3 is a partial tape bearing surface view of a magnetic head havinga write-read-write configuration.

FIG. 4 is a partial tape bearing surface view of a magnetic head havinga read-write-read configuration.

FIG. 5 is a side view of a magnetic tape head with three modulesaccording to one approach where the modules all generally lie alongabout parallel planes.

FIG. 6 is a side view of a magnetic tape head with three modules in atangent (angled) configuration.

FIG. 7 is a side view of a magnetic tape head with three modules in anoverwrap configuration.

FIG. 8 is a partial cross-sectional view of a servo reader transducerstructure according to one approach.

FIG. 9 is a partial cross-sectional view of a servo reader transducerstructure according to one approach.

FIG. 10 is a partial cross-sectional view a servo reader transducerstructure according to one approach.

FIG. 11 is a partial cross-sectional view of a servo reader transducerstructure according to one approach.

FIG. 12 is a partial cross-sectional view of a servo reader transducerstructure and an array of data readers taken along Line 12-12 of FIG.2C.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several configurations of magneticstorage systems having one or more modules which implement writetransducers and TMR servo readers. The servo readers disclosed hereinare tunnel valve transducers, and in some approaches having wider readgaps than would be found on a TMR data reader configured forcompatibility with the same tape format as the servo readers areconfigured for. In an exemplary approach, the TMR servo readers comprisethick layers of alumina and iridium spacing layers between the sensorand the shields, though other materials are also disclosed herein. Thus,various approaches described herein may reduce the probability of sensorshorting for CPP sensors, e.g., such as TMR servo reader sensors, giantmagnetoresistive (GMR) servo reader sensors, etc., as will be describedin further detail below.

In one general approach, an apparatus includes a servo reader transducerstructure on a module. The servo reader transducer structure has a lowershield, an upper shield above the lower shield, the upper and lowershields providing magnetic shielding, a current-perpendicular-to-planesensor between the upper and lower shields, an electrical lead layerbetween the sensor and one of the shields, and a spacer layer betweenthe electrical lead layer and the one of the shields. The electricallead layer is in electrical communication with the sensor. Theconductivity of the electrical lead layer is higher than theconductivity of the spacer layer. An array of writers is also present onthe module. Writer modules having this structure are less susceptible toshorting, and therefore enable use of TMR servo readers on writermodules.

FIG. 1A illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1A, it should be noted that the approaches described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cartridge and are not necessarily part of the drive 100.The tape drive, such as that illustrated in FIG. 1A, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type. Suchhead may include an array of readers, writers, or both.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller 128 via a cable 130. Thecontroller 128, may be or include a processor and/or any logic forcontrolling any subsystem of the drive 100. For example, the controller128 typically controls head functions such as servo following, datawriting, data reading, etc. The controller 128 may operate under logicknown in the art, as well as any logic disclosed herein. The controller128 may be coupled to a memory 136 of any known type, which may storeinstructions executable by the controller 128. Moreover, the controller128 may be configured and/or programmable to perform or control some orall of the methodology presented herein. Thus, the controller may beconsidered configured to perform various operations by way of logicprogrammed into a chip; software, firmware, or other instructions beingavailable to a processor; etc. and combinations thereof.

The cable 130 may include read/write circuits to transmit data to thehead 126 to be recorded on the tape 122 and to receive data read by thehead 126 from the tape 122. An actuator 132 controls position of thehead 126 relative to the tape 122.

An interface 134 may also be provided for communication between the tapedrive 100 and a host (integral or external) to send and receive the dataand for controlling the operation of the tape drive 100 andcommunicating the status of the tape drive 100 to the host, all as willbe understood by those of skill in the art.

FIG. 1B illustrates an exemplary tape cartridge 150 according to oneapproach. Such tape cartridge 150 may be used with a system such as thatshown in FIG. 1A. As shown, the tape cartridge 150 includes a housing152, a tape 122 in the housing 152, and a nonvolatile memory 156 coupledto the housing 152. In some approaches, the nonvolatile memory 156 maybe embedded inside the housing 152, as shown in FIG. 1B. In moreapproaches, the nonvolatile memory 156 may be attached to the inside oroutside of the housing 152 without modification of the housing 152. Forexample, the nonvolatile memory may be embedded in a self-adhesive label154. In one preferred approach, the nonvolatile memory 156 may be aFlash memory device, ROM device, etc., embedded into or coupled to theinside or outside of the tape cartridge 150. The nonvolatile memory isaccessible by the tape drive and the tape operating software (the driversoftware), and/or other device.

By way of example, FIG. 2 illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of the present invention. As shown, the headincludes a pair of bases 202, each equipped with a module 204, and fixedat a small angle α with respect to each other. The bases may be“U-beams” that are adhesively coupled together. Each module 204 includesa substrate 204A and a closure 204B with a thin film portion, commonlyreferred to as a “gap” in which the readers and/or writers 206 areformed. In use, a tape 208 is moved over the modules 204 along a media(tape) bearing surface 209 in the manner shown for reading and writingdata on the tape 208 using the readers and writers. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media supportsurfaces 209 are usually between about 0.1 degree and about 3 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B made of the same orsimilar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), where the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo track readers for reading servo data on the medium.

FIG. 2A illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2A of FIG. 2. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4 to 22 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2A on a one-halfinch wide tape 208. The data bands are defined between servo tracks 210.Each data band may include a number of data tracks, for example 1024data tracks (not shown). During read/write operations, the readersand/or writers 206 are positioned to specific track positions within oneof the data bands. Outer readers, sometimes called servo readers, readthe servo tracks 210. The servo signals are in turn used to keep thereaders and/or writers 206 aligned with a particular set of tracksduring the read/write operations.

FIG. 2B depicts a plurality of readers and/or writers 206 formed in agap 218 on the module 204 in Circle 2B of FIG. 2A. As shown, the arrayof readers and writers 206 includes, for example, 16 writers 214, 16readers 216 and two servo readers 212, though the number of elements mayvary. Illustrative configurations include 8, 16, 32, 40, and 64 activereaders and/or writers 206 per array, and alternatively interleaveddesigns having odd numbers of reader or writers such as 17, 25, 33, etc.An illustrative configuration includes 32 readers per array and/or 32writers per array, where the actual number of transducer elements couldbe greater, e.g., 33, 34, etc. This allows the tape to travel moreslowly, thereby reducing speed-induced tracking and mechanicaldifficulties and/or execute fewer “wraps” to fill or read the tape.While the readers and writers may be arranged in a piggybackconfiguration as shown in FIG. 2B, the readers 216 and writers 214 mayalso be arranged in an interleaved configuration. Alternatively, eacharray of readers and/or writers 206 may be readers or writers only, andthe arrays may contain one or more servo readers 212. As noted byconsidering FIGS. 2 and 2A-B together, each module 204 may include acomplementary set of readers and/or writers 206 for such things asbi-directional reading and writing, read-while-write capability,backward compatibility, etc.

FIG. 2C shows a partial tape bearing surface view of complimentarymodules of a magnetic tape head 200 according to one approach. In thisapproach, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write transducer 214 and the readers, exemplified by the readtransducer 216, are aligned parallel to an intended direction of travelof a tape medium thereacross to form an R/W pair, exemplified by the R/Wpair 222. Note that the intended direction of tape travel is sometimesreferred to herein as the direction of tape travel, and such terms maybe used interchangeable. Such direction of tape travel may be inferredfrom the design of the system, e.g., by examining the guides; observingthe actual direction of tape travel relative to the reference point;etc. Moreover, in a system operable for bi-direction reading and/orwriting, the direction of tape travel in both directions is typicallyparallel and thus both directions may be considered equivalent to eachother.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked magnetoresistive (MR) headassembly 200 includes two thin-film modules 224 and 226 of generallyidentical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe (—), CZTor Al—Fe—Si (Sendust), a sensor 234 for sensing a data track on amagnetic medium, a second shield 238 typically of a nickel-iron alloy(e.g., ˜80/20 at % NiFe, also known as permalloy), first and secondwriter pole tips 228, 230, and a coil (not shown). The sensor may be ofany known type of CPP sensor, including those based on MR, GMR, TMR,etc.

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as ˜45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

The configuration of the tape head 126 according to one approachincludes multiple modules, preferably three or more. In awrite-read-write (W-R-W) head, outer modules for writing flank one ormore inner modules for reading. Referring to FIG. 3, depicting a W-R-Wconfiguration, the outer modules 252, 256 each include one or morearrays of writers 260. The inner module 254 of FIG. 3 includes one ormore arrays of readers 258 in a similar configuration. Variations of amulti-module head include a R-W-R head (FIG. 4), a R-R-W head, a W-W-Rhead, etc. In yet other variations, one or more of the modules may haveread/write pairs of transducers. Moreover, more than three modules maybe present. In further approaches, two outer modules may flank two ormore inner modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. Forsimplicity, a W-R-W head is used primarily herein to exemplifyapproaches (aspects) of the present invention. One skilled in the artapprised with the teachings herein will appreciate how permutations ofthe present invention would apply to configurations other than a W-R-Wconfiguration.

FIG. 5 illustrates a magnetic head 126 according to one approach of thepresent invention that includes first, second and third modules 302,304, 306 each having a tape bearing surface 308, 310, 312 respectively,which may be flat, contoured, etc. Note that while the term “tapebearing surface” appears to imply that the surface facing the tape 315is in physical contact with the tape bearing surface, this is notnecessarily the case. Rather, only a portion of the tape may be incontact with the tape bearing surface, constantly or intermittently,with other portions of the tape riding (or “flying”) above the tapebearing surface on a layer of air, sometimes referred to as an “airbearing”. The first module 302 will be referred to as the “leading”module as it is the first module encountered by the tape in a threemodule design for tape moving in the indicated direction. The thirdmodule 306 will be referred to as the “trailing” module. The trailingmodule follows the middle module and is the last module seen by the tapein a three module design. The leading and trailing modules 302, 306 arereferred to collectively as outer modules. Also note that the outermodules 302, 306 will alternate as leading modules, depending on thedirection of travel of the tape 315.

In one approach, the tape bearing surfaces 308, 310, 312 of the first,second and third modules 302, 304, 306 lie on about parallel planes(which is meant to include parallel and nearly parallel planes, e.g.,between parallel and tangential as in FIG. 6), and the tape bearingsurface 310 of the second module 304 is above the tape bearing surfaces308, 312 of the first and third modules 302, 306. As described below,this has the effect of creating the desired wrap angle α₂ of the taperelative to the tape bearing surface 310 of the second module 304.

Where the tape bearing surfaces 308, 310, 312 lie along parallel ornearly parallel yet offset planes, intuitively, the tape should peel offof the tape bearing surface 308 of the leading module 302. However, thevacuum created by the skiving edge 318 of the leading module 302 hasbeen found by experimentation to be sufficient to keep the tape adheredto the tape bearing surface 308 of the leading module 302. The trailingedge 320 of the leading module 302 (the end from which the tape leavesthe leading module 302) is the approximate reference point which definesthe wrap angle α₂ over the tape bearing surface 310 of the second module304. The tape stays in close proximity to the tape bearing surface untilclose to the trailing edge 320 of the leading module 302. Accordingly,read and/or write elements 322 may be located near the trailing edges ofthe outer modules 302, 306. These approaches are particularly adaptedfor write-read-write applications.

A benefit of this and other approaches described herein is that, becausethe outer modules 302, 306 are fixed at a determined offset from thesecond module 304, the inner wrap angle α₂ is fixed when the modules302, 304, 306 are coupled together or are otherwise fixed into a head.The inner wrap angle α₂ is approximately tan⁻¹(δ/W) where δ is theheight difference between the planes of the tape bearing surfaces 308,310 and W is the width between the opposing ends of the tape bearingsurfaces 308, 310. An illustrative inner wrap angle α₂ is in a range ofabout 0.3° to about 1.1°, though can be any angle required by thedesign.

Beneficially, the inner wrap angle α₂ on the side of the module 304receiving the tape (leading edge) will be larger than the inner wrapangle α₃ on the trailing edge, as the tape 315 rides above the trailingmodule 306. This difference is generally beneficial as a smaller astends to oppose what has heretofore been a steeper exiting effectivewrap angle.

Note that the tape bearing surfaces 308, 312 of the outer modules 302,306 are positioned to achieve a negative wrap angle at the trailing edge320 of the leading module 302. This is generally beneficial in helpingto reduce friction due to contact with the trailing edge 320, providedthat proper consideration is given to the location of the crowbar regionthat forms in the tape where it peels off the head. This negative wrapangle also reduces flutter and scrubbing damage to the elements on theleading module 302. Further, at the trailing module 306, the tape 315flies over the tape bearing surface 312 so there is virtually no wear onthe elements when tape is moving in this direction. Particularly, thetape 315 entrains air and so will not significantly ride on the tapebearing surface 312 of the third module 306 (some contact may occur).This is permissible, because the leading module 302 is writing while thetrailing module 306 is idle.

Writing and reading functions are performed by different modules at anygiven time. In one approach, the second module 304 includes a pluralityof data and optional servo readers 331 and no writers. The first andthird modules 302, 306 include a plurality of writers 322 and no datareaders, with the exception that the outer modules 302, 306 may includeoptional servo readers. The servo readers may be used to position thehead during reading and/or writing operations. The servo reader(s) oneach module are typically located towards the end of the array ofreaders or writers.

By having only readers or side by side writers and servo readers in thegap between the substrate and closure, the gap length can besubstantially reduced. Typical heads have piggybacked readers andwriters, where the writer is formed above each reader. A typical gap is20-35 microns. However, irregularities on the tape may tend to droopinto the gap and create gap erosion. Thus, the smaller the gap is thebetter. The smaller gap enabled herein exhibits fewer wear relatedproblems.

In some approaches, the second module 304 has a closure, while the firstand third modules 302, 306 do not have a closure. Where there is noclosure, preferably a hard coating is added to the module. One preferredcoating is diamond-like carbon (DLC).

In the configuration shown in FIG. 5, the first, second, and thirdmodules 302, 304, 306 each have a closure 332, 334, 336, which extendsthe tape bearing surface of the associated module, thereby effectivelypositioning the read/write elements away from the edge of the tapebearing surface. The closure 332 on the second module 304 can be aceramic closure of a type typically found on tape heads. The closures334, 336 of the first and third modules 302, 306, however, may beshorter than the closure 332 of the second module 304 as measuredparallel to a direction of tape travel over the respective module. Thisenables positioning the modules closer together. One way to produceshorter closures 334, 336 is to lap the standard ceramic closures of thesecond module 304 an additional amount. Another way is to plate ordeposit thin film closures above the elements during thin filmprocessing. For example, a thin film closure of a hard material such asSendust or nickel-iron alloy (e.g., 45/55) can be formed on the module.

With reduced-thickness ceramic or thin film closures 334, 336 or noclosures on the outer modules 302, 306, the write-to-read gap spacingcan be reduced to less than about 1 mm, e.g., about 0.75 mm, or 50% lessthan commonly-used Linear Tape Open (LTO) tape head spacing. The openspace between the modules 302, 304, 306 can still be set toapproximately 0.5 to 0.6 mm, which in some configurations is ideal forstabilizing tape motion over the second module 304.

Depending on tape tension and stiffness, it may be desirable to anglethe tape bearing surfaces of the outer modules relative to the tapebearing surface of the second module. FIG. 6 illustrates an approachwhere the modules 302, 304, 306 are in a tangent or nearly tangent(angled) configuration. Particularly, the tape bearing surfaces of theouter modules 302, 306 are about parallel to the tape at the desiredwrap angle α₂ of the second module 304. In other words, the planes ofthe tape bearing surfaces 308, 312 of the outer modules 302, 306 areoriented at about the desired wrap angle α₂ of the tape 315 relative tothe second module 304. The tape will also pop off of the trailing module306 in this approach, thereby reducing wear on the elements in thetrailing module 306. These approaches are particularly useful forwrite-read-write applications. Additional aspects of these approachesare similar to those given above.

Typically, the tape wrap angles may be set about midway between theapproaches shown in FIGS. 5 and 6.

FIG. 7 illustrates an approach where the modules 302, 304, 306 are in anoverwrap configuration. Particularly, the tape bearing surfaces 308, 312of the outer modules 302, 306 are angled slightly more than the tape 315when set at the desired wrap angle α₂ relative to the second module 304.In this approach, the tape does not pop off of the trailing module,allowing it to be used for writing or reading. Accordingly, the leadingand middle modules can both perform reading and/or writing functionswhile the trailing module can read any just-written data. Thus, theseapproaches are preferred for write-read-write, read-write-read, andwrite-write-read applications. In the latter approaches, closures shouldbe wider than the tape canopies for ensuring read capability. The widerclosures may require a wider gap-to-gap separation. Therefore, apreferred approach has a write-read-write configuration, which may useshortened closures that thus allow closer gap-to-gap separation.

Additional aspects of the approaches shown in FIGS. 6 and 7 are similarto those given above.

A 32 channel version of a multi-module head 126 may use cables 350having leads on the same or smaller pitch as current 16 channelpiggyback LTO modules, or alternatively the connections on the modulemay be organ-keyboarded for a 50% reduction in cable span. Over-under,writing pair unshielded cables may be used for the writers, which mayhave integrated servo readers.

The outer wrap angles α₁ may be set in the drive, such as by guides ofany type known in the art, such as adjustable rollers, slides, etc. oralternatively by outriggers, which are integral to the head. Forexample, rollers having an offset axis may be used to set the wrapangles. The offset axis creates an orbital arc of rotation, allowingprecise alignment of the wrap angle α₁.

To assemble any of the approaches described above, conventional u-beamassembly can be used. Accordingly, the mass of the resultant head may bemaintained or even reduced relative to heads of previous generations. Inother approaches, the modules may be constructed as a unitary body.Those skilled in the art, armed with the present teachings, willappreciate that other known methods of manufacturing such heads may beadapted for use in constructing such heads. With continued reference tothe above described apparatuses, it would be advantageous for taperecording heads to include CPP MR sensor technology, e.g., such as TMRand GMR. Furthermore, with the continued reduction of data track widthsin magnetic storage technologies, CPP MR sensors enable readback of datain ultra-thin data tracks due to their high level of sensitivity in suchsmall operating environments.

As will be appreciated by one skilled in the art, by way of example, TMRis a magnetoresistive effect that occurs with a magnetic tunneljunction. TMR sensors typically include two ferromagnetic layersseparated by a thin insulating barrier layer. If the barrier layer isthin enough e.g., less than about 15 angstroms, electrons can tunnelfrom one ferromagnetic layer to the other ferromagnetic layer, passingthrough the insulating material and thereby creating a current.Variations in the current, caused by the influence of external magneticfields from a magnetic medium on the free ferromagnetic layer of the TMRsensor, correspond to data stored on the magnetic medium.

It is well known that TMR and other CPP MR sensors are particularlysusceptible to shorting during fabrication due to abrasive lappingparticles that scratch or smear conductive material across theinsulating materials separating the conductive leads, e.g., opposingshields, which allow sense (bias) current to flow through the sensor andmagnetic head as a whole. Friction between asperities on the tape andthe ductile metallic films in the sensor gives rise to deformationforces in the direction of tape motion. As a result, an electrical shortis created by the scratching and/or smearing across the layers which hasa net effect of creating bridges of conductive material across thesensor. Particularly, the lapping particles tend to plow through ductilemagnetic material, e.g., from one or both shields, smearing the metalacross the insulating material, and thereby creating an electrical shortthat reduces the effective resistance of the sensor and diminishes thesensitivity of the sensor as a whole.

Scientists and engineers familiar with tape recording technology wouldnot expect a CPP MR sensor to remain operable (e.g., by not experiencingshorting) in a contact recording environment such as tape data storage,because of the near certain probability that abrasive asperitiesembedded in the recording medium will scrape across the thin insulatinglayer during tape travel, thereby creating the aforementioned shorting.

Typical CPP MR sensors such as TMR sensors in hard disk driveapplications are configured to be in electrical contact with the top andbottom shields of read head structures. In such configurations thecurrent flow is constrained to traveling between the top shield and thebottom shield through the sensor, by an insulator layer with a thicknessof about 3 to about 100 nanometers (nm). This insulator layer extendsbelow the hard bias magnet layer to insulate the bottom of the hard biasmagnet from the bottom shield/lead layers, and isolates the edges of thesensor from the hard bias magnet material. In a tape environment, wherethe sensor is in contact with the tape media, smearing of the top orbottom shield material can bridge the insulation layer separating thehard bias magnet from the bottom lead and lower shield, thereby shortingthe sensor. Further, shield deformation or smearing can create aconductive bridge across a tunnel barrier layer in a TMR sensor. Suchtunnel barrier layer may be only 12 angstroms wide or less.

In disk drives, conventional CPP MR designs are acceptable because thereis minimal contact between the head and the media. However, for taperecording, the head and the media are in constant contact. Head coatinghas been cited as a possible solution to these shorting issues; however,tape particles and asperities have been known to scratch through and/orwear away these coating materials as well. Furthermore, conventionalmagnetic recording head coatings are not available for protectingagainst defects during lapping processes, as the coating is appliedafter these process steps. Because the insulating layers of aconventional CPP MR servo reader sensor are significantly thin, thepropensity for electrical shorting due, e.g., to scratches, materialdeposits, surface defects, films deformation, etc., is high. Approachesdescribed herein implement novel spacer layers in combination with TMRservo reader transducer sensors. As a result, some of the approachesdescribed herein may be able to reduce the probability of, or evenprevent, shorting in the most common areas where shorting has beenobserved, e.g. the relatively larger areas on opposite sides of thesensor between the shields.

The potential use of CPP MR servo reader sensors in tape heads hasheretofore been thought to be highly undesirable, as tape heads includemultiple sensors, e.g., 16, 32, 64, etc., on a single die. Thus, if oneor more of those sensors become inoperable due to the aforementionedshorting, the entire head becomes defective and typically would need tobe discarded and/or replaced for proper operation of the apparatus.

Conventional current in-plane type sensors require at least two shortingevents across different parts of the sensor in order to affect thesensor output, and therefore such heads are far less susceptible toshorting due to scratches. In contrast, tape heads with CPP MR servoreader sensors may short with a single event, which is another reasonthat CPP MR servo reader sensors have not been adopted into contactrecording systems.

Scientists and engineers familiar with tape recording technology wouldnot expect a TMR servo reader sensor to remain operable (e.g., by notexperiencing shorting) in a writer module with an array of writetransducers, especially where both TMR servo reader sensors in a pairmust remain operable in order to protect writing operations.

Various approaches described herein comprise a writing module havingscratch resilient TMR servo readers. The writing module comprises zeroor near zero spacing write transducers (also referred to herein as“writers”), where the spacing of the write transducers is into or out ofthe tape bearing surface relative to an imaginary plane extending acrossthe media facing surface of the substrate thereunder. In someapproaches, the TMR servo readers are slightly prerecessed from theplane.

Various approaches include top and/or bottom shields electricallyisolated from a CPP MR servo reader sensor, thereby improving thepreviously experienced issue of shield-to-sensor or shield-to-shieldshorting which caused diminished sensor accuracy and/or totalinoperability. Some of the approaches described herein include spacerlayers as gap liners which are preferably in close proximity to thesensing structure, thereby resisting deformation and thereby thepreviously experienced shorting as well, as will be described in furtherdetail below.

Furthermore, various approaches described herein include TMR servoreaders having a wide read gap comprising thick layers of alumina andiridium spacing layers between the sensors and shields. Servo readersare not constrained by the same processing requirements as data readers,and a wider read gap may be achieved for resisting electrical shortingdue to scratches.

FIG. 8 depicts an apparatus 800, in accordance with one approach. As anoption, the present apparatus 800 may be implemented in conjunction withfeatures from any other approach listed herein, such as those describedwith reference to the other FIGS. However, such apparatus 800 and otherspresented herein may be used in various applications and/or inpermutations which may or may not be specifically described in theillustrative approaches listed herein. Further, the apparatus 800presented herein may be used in any desired environment. Thus FIG. 8(and the other FIGS.) may be deemed to include any possible permutation.

Looking to FIG. 8, apparatus 800 includes a servo reader transducerstructure 802. The servo reader transducer structure 802 may include alower shield 804 above a wafer 803 and optional undercoat 805. Moreover,the servo reader transducer structure 802 may include an upper shield806 positioned above the lower shield 804 (e.g., in a depositiondirection thereof).

A CPP servo sensor 808 (e.g. such as a TMR sensor, GMR sensor, etc.) ispositioned between the upper and lower shields 806, 804. In a preferredconfiguration, the CPP sensor 808 is a tunneling magnetoresistive servosensor. As would be appreciated by one skilled in the art upon readingthe present descriptions, according to preferred approaches, the upperand lower shields 806, 804 provide magnetic shielding for the CPP sensor808. Thus, according to various approaches, one or both of the upper andlower shields 806, 804 may desirably include a magnetic material of atype known in the art. It should be noted that in such approaches, thematerial of the upper and lower shields 806, 804 may vary, oralternatively be the same.

FIG. 8 further includes an upper electrical lead layer 810 positionedbetween the sensor 808 and the upper shield 806 (e.g., the shieldclosest thereto). Moreover, a lower electrical lead layer 812 isincluded between the sensor and the lower shield 804 (e.g., the shieldclosest thereto). The upper and lower electrical lead layers 810, 812are preferably in electrical communication with the sensor 808, e.g., toenable an electrical current to pass through the sensor 808. In oneapproach, an electrical lead layer 810 or 812 may be positioned betweenthe sensor and one of the shields, and the electrical lead layer is inelectrical communication with the sensor. A seed layer for theelectrical lead layer(s) may be present. Preferably, the seed layercomprising chromium, e.g., elemental chromium, a chromium-containingalloy, etc. Illustrative deposition thicknesses for each lead layer,including the seed layer, is in a range of about 10 nm to about 75 nm,but could be higher or lower.

Upper and lower spacer layers 814, 816 are also included in the servoreader transducer structure 802. The spacer layers 814, 816 aredielectric in some approaches, but may be electrically conductive inother approaches. The spacer layers 814, 816 preferably have a very lowductility, e.g., have a high resistance to bending and deformation ingeneral, and ideally a lower ductility than refractory metals such asIr, Ta, and Ti. Upper spacer layer 814 is positioned such that it issandwiched between the upper electrical lead layer 810 and the uppershield 806 (e.g., the shield closest thereto). Similarly, the lowerspacer layer 816 is positioned between the lower electrical lead layer812 and the lower shield 804 (e.g., the shield closest thereto).

In one approach, the thickness of each spacer layer 814, 816 is in therange from about 100 nm to about 150 nm. Experimentation has shown thatservo reader transducer structures having relatively thicker spacerlayers 814, 816 (e.g., from about 100 nm to about 150 nm) show improvedresilience to shorting and improved amplitude in the head.

Although it is preferred that a spacer layer is included on either sideof the sensor 808 along the intended direction of tape travel 852, someapproaches may only include one spacer layer positioned between one ofthe leads and the shield closest thereto, such that at least one of theleads, and preferably both leads, are electrically isolated from theshield closest thereto at the tape bearing surface.

As described above, it is not uncommon for tape asperities passing overthe sensor to smear the material of an upper or lower shield onto theopposite shield, thereby potentially shorting the sensor. Upper andlower spacer layers 814, 816 reduce the probability of a smear occurringin the sensor region. Moreover, because the upper and lower electricallead layers 810, 812 are separated from the upper and lower shields 806,804 at the tape bearing surface by the upper and lower spacer layers814, 816 respectively, the probability of a smear bridging the upper andlower electrical lead layers 810, 812 is minimized.

Thus, as illustrated in FIG. 8, it is preferred that the spacer layers814, 816 are positioned at the media facing surface 850 of the servoreader transducer structure 802, e.g., such that the sensor 808 and/orelectrical lead layers 810, 812 are separated from the upper and lowershields 806, 804, thereby reducing the chance of a shorting eventoccurring. Moreover, it is preferred that the material composition ofthe spacer layers 814, 816 is sufficiently resistant to smearing and/orplowing of conductive material across the sensor 808. Thus, the spacerlayers 814, 816 are preferably hard, e.g., at least hard enough toprevent asperities in the tape passing over the servo reader transducerstructure 802 from causing deformations in the media facing surface 850of the servo reader transducer structure 802 which effect theperformance of the sensor 808. In preferred approaches, the spacerlayers 814, 816 include aluminum oxide. However, according to variousapproaches, the spacer layers 814, 816 may include at least one of thefollowing materials: ruthenium, ruthenium oxide, aluminum oxide, chromeoxide, silicon nitride, boron nitride, silicon carbide, silicon oxide,titanium oxide, titanium nitride, ceramics, etc., and/or combinationsthereof. In some approaches, the spacer layers 814, 816 may be the same.In other approaches, the spacer layers 814, 816 may be different.Illustrative deposition thicknesses of each of the spacer layers, orsub-layers thereof, may be from about 100 nm to about 150 nm.

Furthermore, in various approaches, the electrical lead layers 810, 812may include any suitable conductive material, e.g., which may includeIr, Cu, Ru, Pt, NiCr, Au, Ag, Ta, Cr, etc.; a sandwiched structure of Ta(e.g. Ta/X/Ta); conductive hard alloys such as titanium nitride, boronnitride, silicon carbide, and the like. In a preferred approach, one orboth of the electrical lead layers 810, 812 comprise iridium. In someapproaches, the electrical lead layers 810, 812 be the same. In otherapproaches, the electrical lead layers 810, 812 may be different.

Previously, magnetic heads having aluminum oxide implemented at therecording gap (even amorphous aluminum oxide) were found to have anundesirably low resistance to wear resulting from use, e.g., having amagnetic tape run over the recording gap. Thus, the inventors did notexpect servo reader transducer structures 802 having aluminum oxidespacer layers 814, 816 to exhibit good performance in terms of resistingsmearing and/or plowing caused by tape being run thereover. This ideawas further strengthened in view of the lack of materials and/or layerspresent to promote the growth of crystalline aluminum oxide, the growthof which was thereby not supported. However, in sharp contrast to whatwas expected, the inventors discovered that implementing aluminum oxidespacer layers 814, 816 effectively resisted deformation caused by themagnetic tape. Moreover, experimental results achieved by the inventorssupport this surprising result, which is contrary to conventionalwisdom.

Without wishing to be bound by any theory, it is believed that theimproved performance experienced by implementing aluminum oxide spacerlayers 814, 816 may be due to low ductility of alumina, relatively highhardness, and low friction resulting between the aluminum oxide spacerlayers and defects (e.g., asperities) on a magnetic tape being passedthereover. This is particularly apparent when compared to the higherresistance experienced when metal films and/or coating films areimplemented. Specifically, coatings may not be effective in preventingshorting because underlying films (e.g., such as permalloy) are stillsusceptible to indentation, smearing, plowing, deformation, etc.

Thus, in an exemplary approach, the upper and/or lower spacer layers mayinclude an aluminum oxide which is preferably amorphous. Moreover, anamorphous aluminum oxide spacer layer may be formed using sputtering,atomic layer deposition, etc., or other processes which would beappreciated by one skilled in the art upon reading the presentdescription. According to another exemplary approach, the upper and/orlower spacer layers may include an at least partially polycrystallinealuminum oxide.

A distance between the upper and lower shields 806, 804 along the tapebearing surface is denoted by a distance d. In a preferred approach, thedistance between the upper and lower shields 806, 804 along the tapebearing surface is at least 300 nm. In more approaches, the distancebetween the upper and lower shields 806, 804 is in a range of about 300nm to about 500 nm. This range is contrasted to data readers in the samedrive, which preferably have a shield-to-shield distance lower than thisrange to provide high resolution.

In a preferred approach, the shield-to-shield spacing provides a widegap for increased immunity to shorting caused by smearing. A wider gapresults in higher amplitudes due to the relatively lower frequency ofservo readers compared to the frequency of a data signal.Experimentation shows that a wide gap in the preferred range (e.g.,about 300 nm to about 500 nm) results in improved servo patterndetection. This improvement is especially significant for chevronpattern angles of 15 degrees or greater. Wider gaps also enable locatingthe sensors closer to the tape due to the increased scratch shortingresistance. Lower head tape spacing improves the writing quality.

Although upper and lower spacer layers 814, 816 separate upper and lowerelectrical lead layers 810, 812 from the upper and lower shields 806,804, respectively, at the media facing surface 850 of the servo readertransducer structure 802, the upper and/or lower electrical lead layers810, 812 are preferably still in electrical communication with theshield closest thereto.

The module (not shown) having the servo reader transducer structure 802may include an array of writers thereon. The writers may be configuredand/or arranged according to descriptions of writers described elsewhereherein and/or in other FIGS. The writers may comprise write poles asdiscussed in other approaches including FIG. 2. In one approach, thewrite poles of the writers are not recessed from a plane of the mediafacing surface 850 of the module. The tape bearing surface 850 of themodule generally extends along the media facing side of the substrateand the closure. The current-perpendicular-to-plane servo sensor 808 isrecessed from the plane of the media facing surface 850 of the module insome configurations. For example, where the servo sensor transducerstructure is on a common module with an array of writers, a recession ofthe servo sensor 808 from the plane of the media facing surface 850 ofthe module is about 5 nm or less.

In another approach, depicted in FIG. 12, the module 1200 having theservo reader transducer structure 802 may include an array of datareaders 1202 thereon. The data readers may be configured and/or arrangedaccording to descriptions of writers described elsewhere herein and/orin other FIGS. In this and other approaches, the servo sensors 808 mayhave zero or slight recession from the plane of the media facing surface850. Preferably, the sensors 1204 of the data readers 1202 are morerecessed from the plane of the media facing surface 850 than the servosensors 808, as the servo sensors 808 presented herein are lesssusceptible to shorting than the data sensors 1204.

The upper shield 804 may be formed using any fabrication technique thatwould be appreciated by one skilled in the art upon reading the presentdescriptions. For example, the upper shield 804 may be formed using,e.g., plating, sputtering, etc. Plating techniques may be reserved forfilms thicker than 0.3 microns according to one approach.

Approaches which include CPP sensors may include an electricalconnection to a magnetic lamination or layer proximate to the sensor, toa spacer layer 814, 816 positioned between the sensor structure 808 andone or both magnetic shields 804, 806, and/or to the sensor 808 itself.For example, such approaches may include an electrical lead proximate tothe sensor for enabling current flow through the sensor structure. Suchleads may be an extension of a layer itself, or a separately-depositedmaterial. Establishing an electrical connection to a magnetic laminationproximate to the sensor and/or to the spacer itself may create aconfiguration in which portions of the magnetic shields of an apparatusare not biased or current-carrying e.g. the shields are “floating”. Insuch approaches, the nonmagnetic spacer layer 814, 816 included betweenthe sensor structure 808 and the magnetic shields 804, 806 may serve asan electrical lead. These portions may be biased according to variousapproaches.

The electrical lead layers 810, 812 may or may not be in electricalcommunication with the associated shield. In approaches where the spacerlayers 814, 816 are insulative, various mechanisms for providing currentto the sensor may be implemented. Looking to FIG. 8, upper and lowerelectrical lead layers 810, 812 are in electrical communication with theupper and lower shields 806, 804 respectively, by implementing studs818, 819 at a location recessed from the media facing surface 850.

Studs 818, 819 preferably include one or more conductive materials,thereby effectively providing an electrical via through insulativespacer layers 814, 816 which allows current to flow between the shields806, 804 and electrical lead layers 810, 812, respectively. Thus,although insulative spacer layers 814, 816 may separate the shields 806,804 from the electrical lead layers 810, 812 and sensor 808, the studs818, 819 allow current to flow from one shield to the other through thesensor. According to an exemplary in-use approach, which is in no wayintended to limit the invention, the servo reader transducer structure802 may achieve this functionality by diverting current from lowershield 804 such that it passes through stud 819 (the stud closestthereto) and into the lower electrical lead 812. The current thentravels towards the media facing surface 850 along the lower electricallead 812, and preferably passes through the tunneling sensor 808 nearthe media facing surface 850. As will be appreciated by one skilled inthe art, the strength of a signal transduced from the magnetictransitions on a magnetic recording medium decreases along the sensor inthe height direction (perpendicular to the media facing side). Thus, itis preferred that at least some of the current passes through the sensor808 near the media facing surface 850, e.g., to ensure high sensoroutput. According to one approach, this may be accomplished by achievingideally an approximate equipotential along the length of the sensor 808.

Studs 818, 819 preferably have about the same thickness as upper andlower spacer layers 814, 816 respectively. Moreover, studs 818, 819 arepreferably positioned behind or extend past an end of the sensor 808which is farthest from the media facing surface 850.

The electrically conductive layer(s) preferably have a higherconductivity than the spacer layer. Thus, the spacer layer in someapproaches may be electrically insulating or a poor conductor. Thishelps ensure that a near equipotential is achieved along the length ofthe sensor. Also and/or alternatively, the resistance of the electricallead layer along a direction orthogonal to a media facing surface may beless than a resistance across the sensor along a direction parallel tothe media facing surface in some approaches. This also helps ensure thata near equipotential is achieved along the length of the sensor. Infurther approaches, the product of the spacer layer thickness multipliedby the conductivity of the spacer layer is less than a product of theelectrical lead layer thickness multiplied by the conductivity of theelectrical lead layer associated with the spacer layer, e.g., positionedon the same side of the sensor therewith.

Achieving near equipotential along the length of the sensor 808 resultsin a relatively more uniform current distribution along the length ofthe sensor 808 in the height direction. Although equipotential ispreferred along the length of the sensor 808, a 20% or less differencein the voltage drop (or loss) across the sensor 808 at the media facingsurface 850 compared to the voltage drop across the end of the sensor808 farthest from the media facing surface 850 may be acceptable, e.g.,depending on the desired approach. For example, a voltage drop of 1 Vacross the sensor 808 at the media facing surface 850 compared to avoltage drop of 0.8 V across the end of the sensor 808 farthest from themedia facing surface 850 may be acceptable.

Although the operating voltage may be adjusted in some approaches tocompensate for differences in the voltage drop along the length of thesensor 808 of greater than about 10%, it should be noted that theoperating voltage is preferably not increased to a value above athreshold value. In other words, increasing the operating voltage abovea threshold value is preferably not used to bolster the voltage dropacross the sensor 808 at the media facing surface 850 to a desired level(e.g., sensitivity) when a servo reader transducer structure 802 has adrop of greater than about 10%. The threshold value for the operatingvoltage of a given approach may be predetermined, calculated in realtime, be set in response to a request, etc. According to someapproaches, the threshold value for the operating voltage may bedetermined using breakdown voltage(s) of the servo reader transducerstructure 802 layers, e.g., based on their material composition,dimensions, etc.

In some approaches, differences in resistivity may also be used tominimize the voltage drop along the length of the sensor 808. In orderto ensure that sufficient current passes through the sensor 808 near themedia facing surface 850, it is preferred that the resistivity of thesensor 808, as for example due to tunnel barrier resistivity in a TMR,is high relative to the resistivity of the electrical lead layers 810,812. By creating a difference in the relative resistance of the adjacentlayers, low voltage drop may desirably be achieved along the height ofthe sensor 808.

This relative difference in resistivity values may be achieved byforming the sensor 808 such that it has a relatively high barrierresistivity, while the electrical lead layers 810, 812 may have a higherthickness, thereby resulting in a lower resistance value. It should benoted that the thickness of the electrical lead layers 810, 812 ispreferably greater than about 5 nm. The bulk resistivity of a givenmaterial typically increases as the dimensions of the materialdecreases. As will be appreciated by one skilled in the art upon readingthe present description, the resistivity of a material havingsignificantly small dimensions may actually be higher than for the samematerial having larger dimensions, e.g., due to electron surfacescattering. Moreover, as the thickness of the electrical lead layers810, 812 decreases, the resistance thereof increases. Accordingly, thethickness of the upper and/or lower electrical lead layers 810, 812 ispreferably between about 2 nm and about 20 nm, more preferably betweenabout 5 nm and about 15 nm, still more preferably less than about 15 nm,but may be higher or lower depending on the desired configuration, e.g.,depending on the material composition of the upper and/or lowerelectrical lead layers 810, 812. Moreover, the thicknesses (in thedeposition direction) of the upper and/or lower spacer layers 814, 816are preferably between about 5 nm and about 50 nm, but may be higher orlower depending on the desired configuration. For example, spacer layershaving a relatively hard material composition may be thinner than spacerlayers having a material composition which is less hard.

With continued reference to FIG. 8, studs 818, 819 may be implementedduring formation of the servo reader transducer structure 802, usingprocesses which would be apparent to one skilled in the art upon readingthe present description. According to an example, which is in no wayintended to limit the invention, the spacer layer may be formed over amask (e.g., using sputtering or other forms of deposition), therebycreating a void in the spacer layer upon removal of the mask.Thereafter, the stud may be formed in the void, e.g., using sputteringor plating, after which the stud may be planarized. However, accordingto another example, a spacer layer may be formed full film, after whicha via may be created, e.g., using masking and milling, and filling thevia with the stud material, e.g., using ALD, after which the stud mayoptionally be planarized. Moreover, it should be noted that insulatinglayer 822 may be thicker than sensor 808, thereby causing upperelectrical lead layer 810 and upper spacer layer 814 to extend in theintended tape travel direction 852 before continuing beyond the edge ofthe sensor 808 farthest from the media facing surface 850, e.g., as aresult of manufacturing limitations, as would be appreciated by oneskilled in the art upon reading the present description.

Thus, the spacer layers 814, 816 in combination with the studs 818, 819may provide protection against smearing at the media facing surface 850while also allowing for the shields 806, 804 to be in electricalcommunication with the electrical lead layers 810, 812. It follows thatone or both of the shields 806, 804 may serve as electrical connectionsfor the servo reader transducer structure 802. According to the presentapproach, the shields 806, 804 function as the leads for the servoreader transducer structure 802. Moreover, the current which flowstowards the media facing surface 850 tends to generate a magnetic fieldwhich is canceled out by the magnetic field created by the current whichflows away from the media facing surface 850.

However, it should be noted that the approach illustrated in FIG. 8 isin no way intended to limit the invention. Although the electrical leadlayers 810, 812 depicted in FIG. 8 are electrically connected to upperand lower shields 806, 804 respectively, in other approaches, one orboth of the electrical lead layers 810, 812 may not be electricallyconnected to the respective shields. According to one example, the upperand lower electrical lead layers may be stitched leads, e.g., see FIG.10 and FIG. 11, rather than each of the lead layers 810, 812 having asingle lead as seen in FIG. 8, as will soon become apparent. Thus,neither of the upper or lower electrical lead layers may be inelectrical communication with the shields according to some approaches,as will be described in further detail below.

According to one configuration of apparatus 800, a drive mechanism (notshown) may be implemented for passing a magnetic medium over the sensor808. In one aspect, a controller may be electrically coupled to thesensor 808 e.g., as described with reference to other FIGS., includingFIG. 1A.

FIG. 9 depicts an apparatus 900, in accordance with one approach. As anoption, the present apparatus 900 may be implemented in conjunction withfeatures from any other approach listed herein, such as those describedwith reference to the other FIGS. However, such apparatus 900 and otherspresented herein may be used in various applications and/or inpermutations which may or may not be specifically described in theillustrative approaches listed herein. Further, the apparatus 900presented herein may be used in any desired environment. Thus FIG. 9(and the other FIGS.) may be deemed to include any possible permutation.Various components of FIG. 9 have common numbering with similarcomponents of FIG. 8.

The apparatus 900 includes a servo reader transducer structure 902.According to one aspect of apparatus 900 depicted in FIG. 9, only asingle hard spacer layer 816 is present. In this approach, the hardspacer layer 816 is between the sensor 808 and the lower shield 804. Aconductive conventional spacer layer 932 is present between the sensor808 and the upper shield 806.

Looking to FIG. 10, an apparatus 1000 includes a servo reader transducerstructure 1002 in accordance with various approaches. As an option, thepresent apparatus 1000 may be implemented in conjunction with featuresfrom any other configuration listed herein, such as those described withreference to the other FIGS. Specifically, for example, FIG. 10illustrates variations of the approach of FIG. 8 depicting severalexemplary configurations within the servo reader transducer structure1002. Accordingly, various components of FIG. 10 have common numberingwith those of FIG. 8.

However, such apparatus 1000 and others presented herein may be used invarious applications and/or in permutations which may or may not bespecifically described in the illustrative approaches listed herein.Further, the apparatus 1000 presented herein may be used in any desiredenvironment. Thus FIG. 10 (and the other FIGS.) may be deemed to includeany possible permutation.

Looking to FIG. 10, apparatus 1000 includes a servo reader transducerstructure 1002 having spacer layers 814, 816 sandwiched between shields806, 804 and electrical lead layers 1004, 1006 respectively. However,unlike the approach illustrated in FIG. 8, upper and lower electricallead layers 1004, 1006 of the present approach may not be in electricalcommunication with either of the shields 806, 804. Rather, when thespacer layers 814, 816 are insulating and fully isolate electrical leadlayers 1004, 1006 from upper and lower shields 806, 804 respectfullyalong the lengths (perpendicular to the media facing surface 850)thereof. Thus, a current (e.g., a read sense current) does not passthrough at least one of the upper and lower shields from the CPP sensor808 and/or electrical lead layers 1004, 1006. In other words, theelectrical connection to one or both of the electrical lead layers 1004,1006 may be independent. As mentioned above, upper and/or lower spacerlayers 814, 816 may include at least one of the following materials:ruthenium, ruthenium oxide, aluminum oxide, chrome oxide, siliconnitride, boron nitride, silicon carbide, silicon oxide, titanium oxide,an amorphous aluminum oxide, etc., and/or combinations thereof, andconducting but non-smearing materials such as titanium nitride,conductive ceramics, etc.

According to some approaches, the at least one of the upper and lowershields 806, 804 not having a current (e.g., a read sense current)passing therethrough may be coupled to a bias voltage source. In otherwords, at least one of the upper and lower shields 806, 804 may becoupled to a bias voltage source. According to other approaches, one orboth of the shields may be coupled to an electrical connection (e.g., alead), but may not carry any current therethrough.

As mentioned above, at least one of the upper and lower electrical leadlayers may be a stitched lead. According to the present configuration,which is in no way intended to limit the invention, both electrical leadlayers 1004, 1006 are stitched leads which include a main layer 1008,1010 and a preferably thicker stitch layer 1012, 1014 thereon,respectively. Vias 1013, 1015 may be coupled to a respective electricallead layer 1004, 1006. The main layers 1008, 1010 may be made duringformation of the servo reader transducer structure 1002, while stitchlayers 1012, 1014 may be drilled and backfilled after formation of theservo reader transducer structure 1002 using processes and/or in adirection which would be apparent to one skilled in the art upon readingthe present description.

As shown, the stitch layers 1012, 1014 are preferably recessed from amedia facing side of the main layer 1008, 1010, e.g., the side closes tothe media facing surface 850. By stitching a second layer of leadmaterial, e.g. the stitch layer 1012, 1014, which is preferably recessedbeyond a back edge 1016 of the sensor 808 in the height direction H, theresistance associated with the electrical lead layers 1004, 1006 maydesirably be reduced, e.g., relative to routing either of the leads pasta back edge of the respective shield. In various approaches, the mainlayers 1008, 1010 and/or stitch layers 1012, 1014 of either of thestitched electrical lead layers 1004, 1006 may be constructed of anysuitable conductive material, e.g., which may include Ir, Cu, Ru, Pt,NiCr, Au, Ag, Ta, Cr, etc.; a laminated structure of Ta (e.g. Ta/X/Ta);etc.

As mentioned above, the stitched electrical lead layer configurationimplemented in servo reader transducer structure 1002 desirably reducesthe resistance associated with the routing either of the leads beyond aback edge of the respective shield. For example, in an aspect where Ruis used as the top lead material, the resistivity “p” would be about 7.1micro-ohms/cm. A single lead with thickness of 30 nm would have a sheetresistivity (p/thickness) equal to about 2.3 ohms/square. This impliesthat if the top lead design had 6 “squares” of lead geometry, the leadresistance would be about 13.8 ohms. However, by implementing a stitchedlayer above the main layer of the stitched electrical lead layer, thetotal lead resistance would be significantly reduced. For example,consider a stitched lead of Ru with a thickness of 45 nm covering 5 ofthe 6 “squares” of the lead geometry. The lead region where the stitchedstructure and the initial lead overlay has a net thickness of about 75nm and a sheet resistivity equal to 0.95 ohms/square. Implementing astitched electrical lead layer as described above would reduce the leadresistance to 7.3 ohms or by about 45%. Aspects described herein may ormay not implement the stitched electrical lead layers 1004, 1006 (e.g.,see FIG. 8), depending on the preferred approach.

In still further approaches, one or more of the electrical lead layersmay be an extension of a layer itself, or a separately-depositedmaterial. Establishing an electrical connection to a magnetic laminationproximate to the sensor may create a configuration in which portions ofthe magnetic shields of an apparatus are not biased or current-carrying.In such approaches, the electrical lead layers included between thesensor structure and the magnetic shield may serve as an electricallead. Moreover, at least one of the upper and lower shields 806, 804 maybe a floating shield, and thereby may not be biased or current-carrying.

Looking to FIG. 11, an apparatus 1100 is depicted and includes a servoreader transducer structure 1102 in accordance with various approaches.As an option, the present apparatus 1100 may be implemented inconjunction with features from any other approach listed herein, such asthose described with reference to the other FIGS. Specifically, forexample, FIG. 11 illustrates variations of the configuration of FIG. 8depicting several exemplary configurations within the servo readertransducer structure 1002. Accordingly, various components of FIG. 11have common numbering with those of FIG. 8.

However, such apparatus 1100 and others presented herein may be used invarious applications and/or in permutations which may or may not bespecifically described in the illustrative approaches listed herein.Further, the apparatus 1100 presented herein may be used in any desiredenvironment. Thus FIG. 11 (and the other FIGS.) may be deemed to includeany possible permutation.

FIG. 11 depicts an apparatus 1100 which includes vias 1013, 1015 likethose of FIG. 10, and studs 818, 819 like those in FIG. 8. The studs818, 819 are not current carrying and therefore preferably have arelatively high resistance compared to the current-carrying portions ofthe head.

According to an exemplary in-use approach, which is in no way intendedto limit the invention, the servo reader transducer structure 1102 mayachieve this functionality by diverting current from lower shield 804such that it passes through stud 819 (the stud closest thereto, asdescribed in FIG. 8) and into the via 1015 coupled to the lowerelectrical lead layer 1006 (e.g. as described in FIG. 10). The currentthen travels towards the media facing surface 850 along the lowerelectrical lead 1006, and preferably passes through the tunneling sensor808 near the media facing surface 850. As will be appreciated by oneskilled in the art, the strength of a signal transduced from themagnetic transitions on a magnetic recording medium decreases along thesensor in the height direction (perpendicular to the media facing side).Thus, it is preferred that at least some of the current passes throughthe sensor 808 near the media facing surface 850, e.g., to ensure highsensor output. According to one approach, this may be accomplished byachieving ideally an approximate equipotential along the length of thesensor 808.

Various approaches described herein are able to provide bi-directionalprotection for CPP transducers against shorting which may otherwiseresult from passing magnetic media over such transducers. Implementing aspacer layer having a high resistivity to smearing and/or plowingbetween the CPP servo reader transducer layer and each of the conductinglead portions of the transducer stack without hindering the flow ofcurrent through the sensor enables the approaches herein to maintaindesirable performance over time. Moreover, as previously mentioned,although it is preferred that a spacer layer is included on either sideof a sensor along the intended direction of tape travel, some of theapproaches described herein may only include one spacer layer positionedbetween one of the leads or sensor and the shield closest thereto, suchthat the at least one lead is electrically isolated from the shieldclosest thereto.

Various configurations may be fabricated using known manufacturingtechniques. Conventional materials may be used for the various layersunless otherwise specifically foreclosed. Furthermore, as describedabove, deposition thicknesses, configurations, etc. may vary dependingon the approach.

It should be noted that although FIGS. 8-9 each illustrate a singleservo reader transducer structure (servo reader transducer structures802, 902, 1002, 1102), various approaches described herein include morethan one servo reader transducer structures above a common substrate,e.g., as shown in FIG. 2B. Furthermore, the number of servo readertransducer structures in a given array may vary depending on thepreferred approach.

In various approaches, a module e.g., as shown in any of FIGS. 2-7 mayinclude a servo reader transducer structure according to any approachdescribed herein, and may further include an array of writers thereon,an array of data readers thereon, or arrays of data readers and writersthereon. The readers and/or writers may be of any type known in the art,and may be configured and/or arranged according to descriptions ofwriters described elsewhere herein and/or in other FIGS.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

It will be further appreciated that aspects of the present invention maybe provided in the form of a service deployed on behalf of a customer.

The inventive concepts disclosed herein have been presented by way ofexample to illustrate the myriad features thereof in a plurality ofillustrative scenarios, approaches, and/or implementations. It should beappreciated that the concepts generally disclosed are to be consideredas modular, and may be implemented in any combination, permutation, orsynthesis thereof. In addition, any modification, alteration, orequivalent of the presently disclosed features, functions, and conceptsthat would be appreciated by a person having ordinary skill in the artupon reading the instant descriptions should also be considered withinthe scope of this disclosure.

While various approaches have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an approach of the presentinvention should not be limited by any of the above-described exemplaryapproaches, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. An apparatus, comprising: a servo readertransducer structure on a module, the servo reader transducer structurehaving: a lower shield; an upper shield above the lower shield, theupper and lower shields providing magnetic shielding, wherein a distancebetween the shields is at least 300 nm; a current-perpendicular-to-planesensor between the upper and lower shields; a first electrical leadlayer between the sensor and one of the shields, wherein the electricallead layer is in electrical communication with the sensor; a firstspacer layer between the electrical lead layer and the one of theshields, wherein a conductivity of the electrical lead layer is higherthan a conductivity of the spacer layer; and an array of data readers onthe module adjacent the servo reader transducer structure, wherein thecurrent-perpendicular-to-plane sensor is recessed from a plane of amedia facing surface of the module, and sensors of the data readers aremore recessed from the plane of the media facing surface of the modulethan the current-perpendicular-to-plane sensor of the servo readertransducer structure.
 2. An apparatus as recited in claim 1, wherein thefirst electrical lead layer is present between thecurrent-perpendicular-to-plane sensor and the upper shield, and furthercomprising a second electrical lead layer, wherein the second electricallead layer is present between the current-perpendicular-to-plane sensorand the lower shield, wherein the first spacer layer is present betweenthe upper shield and the first electrical lead layer, wherein a secondspacer layer is present between the lower shield and the secondelectrical lead layer.
 3. An apparatus as recited in claim 1, whereinthe spacer layer includes at least one material selected from the groupconsisting of: ruthenium, ruthenium oxide, aluminum oxide, chrome oxide,silicon nitride, boron nitride, silicon carbide, silicon oxide, titaniumoxide, and titanium nitride.
 4. An apparatus as recited in claim 3,wherein the spacer layer includes amorphous aluminum oxide.
 5. Anapparatus as recited in claim 3, wherein the spacer layer includes atleast partially polycrystalline aluminum oxide.
 6. An apparatus asrecited in claim 3, wherein the spacer layer includes aluminum oxidehaving a deposition thickness of about 100 nm to about 150 nm.
 7. Anapparatus as recited in claim 1, wherein the electrical lead layerincludes a main layer and a stitch layer thereon, the stitch layer beingrecessed from a media facing side of the main layer.
 8. An apparatus asrecited in claim 1, wherein a resistance of the electrical lead layeralong a direction orthogonal to the media facing surface of the moduleis less than a resistance across the current-perpendicular-to-planesensor along a direction parallel to the media facing surface of themodule.
 9. An apparatus as recited in claim 1, wherein the spacer layeris electrically insulating.
 10. An apparatus as recited in claim 1,wherein the electrical lead layer is in electrical communication withthe one of the shields.
 11. An apparatus as recited in claim 1, whereinthe electrical lead layer is not in electrical communication with theone of the shields.
 12. An apparatus as recited in claim 1, wherein thecurrent-perpendicular-to-plane sensor is a tunneling magnetoresistiveservo sensor.
 13. An apparatus as recited in claim 1, wherein theelectrical lead layer comprises iridium.
 14. An apparatus as recited inclaim 13, wherein a total deposition thickness of the iridium is in arange of about 10 nm to about 75 nm.
 15. An apparatus as recited inclaim 1, comprising a seed layer for the electrical lead layer, the seedlayer comprising chromium.
 16. An apparatus as recited in claim 1,wherein a distance between the shields is in a range of about 300 nm toabout 500 nm.
 17. An apparatus as recited in claim 1, wherein arecession of the current-perpendicular-to-plane sensor from the plane ofthe media facing surface of the module is about 5 nm to about 1 nm. 18.An apparatus as recited in claim 1, comprising: a drive mechanism forpassing a magnetic medium over the module; and a controller electricallycoupled to the module.